This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. The purpose of this collaboration is to develop the means to image live cells with micron resolution by means of ESR microscopy. This can provide the distribution of intra or extra cellular oxygen levels as a means to provide better understanding of cell metabolism and to aid in medical diagnostics. It would also be possible to study cell migration in the blood or interstitial fluid, which is important in various physiological environments. The use of specially modified trityls which can enter the cell will be important for this study.